Coordinated Multiple Input Multiple Output (abbreviated as MIMO) technology, also referred to as Coordinated Multi-point transmission and reception (COMP) technology, is to use coordinated transmission of transmitting antennae within a plurality of cells to improve the capacity of the wireless links at the cell edge and the transmission reliability, which can effectively solve the cell edge interference problem.
In wireless communication, if a plurality of antennae are used at the transmitting end (such as base station eNB), the transmission rate can be improved using the manner of spatial multiplexing, i.e., different data are transmitted at different antenna locations on the same time frequency resource at the transmitting end, and a plurality of antennae are also used at the receiving end (user equipment UE). Generally speaking, MIMO has two transmission forms: one is Single User-MIMO (abbreviated as SU-MIMO), which is to allocate all the antenna resources to the same user in the case of a single user; another is Multiple User-MIMO (abbreviated as MU-MIMO), which is to allocate the resources of different antenna spaces to different users in the case of multiple users and to achieve serving a plurality of users at the same time and on the same carrier by way of spatial distinction, and the average throughput within the cell can be improved by way of the MU-MIMO transmission form.
In particular, SU-MIMO refers to one user equipment alone occupying the physical resources allocated to the user equipment within one transmission interval. MU-MIMO refers to one user equipment and at least one other user equipment sharing the physical resources allocated to the user equipment within one transmission interval. One user equipment and some other user equipments share the same physical resource (including time frequency resource) by way of space division multiple-access or space division multiplexing.
In the long-term evolution (abbreviated as LTE) of the 3rd Generation Partnership Project, the user equipment is deployed to be based on one of the following transmission modes by way of high layer signaling semi-statically, and as to version 8, the following modes are included:
Mode 1: Single-antenna port; port 0
Mode 2: Transmit diversity
Mode 3: Open-loop spatial multiplexing
Mode 4: Closed-loop spatial multiplexing
Mode 5: Multi-user MIMO
Mode 6: Closed-loop Rank=1 pre-coding
Mode 7: Single-antenna port; port 5
The UE determines different transmission formats of the channel state information according to different transmission modes, and then the transmitting end (i.e., eNB) carries out scheduling according to the channel state information fed back by the UE and configures new channel state information for actual transmission based on a certain principle (such as maximum capacity principle). In this case, the channel state information fed back by the UE includes:
Channel Quality Indication information (abbreviated as CQI) is an indicator measuring the quality of a downlink channel. In the 36-213 specification, CQI is represented using integral values of 0-15, which represent the levels of different CQIs respectively, and different CQIs have their own corresponding modulation and coding scheme (MCS).
The pre-coding matrix indicator (abbreviated as PMI) is an index number of a pre-coding codebook fed back by the UE. Under three modes such as Closed loop spatial multiplexing, MU-MIMO, and Closed-loop RI=1, the PMI information needs to be fed back, and the PMI information does not need to be fed back under other transmission modes. The feedback granularity of PMI can be that the whole bandwidth feeds back one PMI or that the PMI is fed back according to a subband.
Rank indicator (abbreviated as RI) is used for describing the number of spatially independent channels and corresponds to the rank of a channel response matrix. Under the Open loop spatial multiplexing and Closed loop spatial multiplexing, the UE needs to feed back RI information, and it does not need to feed back RI information under other modes. The rank of a channel matrix corresponds to the number of layers.
Since the feedback transmission method of the channel state information has a significant impact on the precision of the feedback information, it plays an important role for the transmitting end to perform correct resource scheduling and improve the transmission performance of the wireless system. However, the definition of the contents carried by the channel state information in the prior art are only suitable for the case of single user-MIMO, or only suitable for the case of multiple user-MIMO, but it is not suitable for those transmission modes under which a multiple user-MIMO and a single user-MIMO can be switched from one to another.